As a pretreatment for microscope observation of a tissue piece collected from a living thing (also called a specimen), there is used a sample preparation method of applying a fixing treatment, a dehydrating treatment, a degreasing treatment, a penetration (embedding) treatment to the tissue piece in this order. This sample preparation method is performed by immersing the tissue piece into various kinds of liquid chemical. For example, as liquid chemicals, formalin (fixing agent) is used in the fixing treatment, alcohol (dehydrating agent) is used in the dehydrating treatment, xylene (intermediate agent or degreasing agent) is used in the degreasing treatment, and paraffin (embedding agent) is used in the penetration treatment.
Japanese Patent Laid-Open No. 2009-281745 (PTL 1) describes a tissue piece treating apparatus capable of continuing treatment operation by replenishing a liquid chemical even if the liquid chemical supplied to a treatment tank runs short.
Further, Japanese Patent Laid-Open No. 2010-78471 (PTL 2) describes a tissue piece treating apparatus capable of reusing a liquid chemical which becomes unable to apply treatment to a tissue piece, as a cleaning liquid.